AB1023 THE DIFFERENTIAL CHARACTERISTIC OF SPONDYLOARTHRITIS PATIENTS WHO CANNOT BE CLASSIFIED ACCORDING TO ASAS: RESULTS FROM THE GESPA COLOMBIAN COHORT
Authors: G. Rodríguez Salas, A. M. Santos, V. Navarro-Compán, M. J. Mantilla, I. Rueda, J. C. Santacruz Devia, S. Arias, J. Rueda, J. G. Ballesteros, E. Calvo, M. Cardiel, C. F. Pacheco Tena, J. Londono
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> The Assessment of SpondyloArthritis International Society (ASAS) classification criteria for SpA has changed the approach to the disease, enhancing the performance of the classification process. However, regardless of the ASAS classification criteria were developed according to a global cohort of patients, Latin American patients were not included in a significant number. SpA patients from our region have unique characteristics that may impact the SpA classification. Other alleles than HLA-B27 have been identified, the frequency of HLA-B15 was reported to be 19.1% in the Latin American SpA population [1], compared to 3.3% in the healthy population [2]. <h3>Objectives</h3> The aims of our study were to describe the demographics, clinical, genetic characteristics, and metrology of patients diagnosed with SpA by a rheumatologist but who did not meet ASAS classification criteria and compare them to patients who fulfilled ASAS classification criteria. <h3>Methods</h3> A longitudinal and analytic study was conducted on a cohort of Colombian SpA patients. Patients were evaluated in a SpA clinic at two institutions from 1990 to the present. All patients were classified according to ASAS. Patients included before 2011 were reclassified according to ASAS by a group of two rheumatologists. <h3>Results</h3> We enrolled 473 SpA patients; of these, 437 (92.39%) fulfilled ASAS classification criteria, and 37 (7.6%) had a diagnosis by rheumatologists but did not fulfil ASAS classification criteria for neither axial or peripheral SpA. There were no differences in gender distribution between both groups (table 1). Patients who did not fulfill ASAS classification had a lower frequency of enthesitis (36.1% vs. 79.2%, P = 0.00), dactylitis (5.6% vs. 19%, P = 0.04), arthritis (30.6 vs. 71.6%, P = 0.00), and lower frequency of history of infections preceding SpA onset (2.8% vs. 27.9%, P = 0.01) than patients classified by ASAS, respectively. There were no differences in the frequency of uveitis, psoriasis, inflammatory spinal pain, or familiar history of SpA (P = 0.3). The frequency of SpA with axial symptoms at the onset of the disease was higher in patients unclassified by ASAS (Table 1). Non-ASAS SpA patients had a higher frequency of HLA-B15 (25% vs. 11.8%, P = 0.01), and lower frequency of HLA-B27 (16.7% vs. 48.2%, P = 0.01) than ASAS SpA patients, respectively (Graphic 1). The BASFI and BASDAI were comparable between two groups (Table 1) <h3>Conclusion</h3> Most patients diagnosed as SpA by rheumatologists in a Colombian cohort fulfilled ASAS classification criteria. Only 7% did not fulfil the criteria. Of these patients, the demographic characteristics, disease activity and functional compromise were comparable to patients classified by ASAS. Interestingly, the frequency of HLA-B15 is high in both groups, but it is significantly higher in unclassified individuals. These results highlight the significance of HLA alleles other than HLA-B27 and their potential diagnostic value for SpA in LatinAmerica. <h3>References</h3> [1]Londono J, Santos AM, et al (2015) Analysis of HLA-B15 and HLA-B27 in spondyloarthritis with peripheral and axial clinical patterns. BMJ Open 5:e009092. https://doi.org/10.1136/bmjopen-2015-009092 [2]Arias-Murillo YR, Castro-Jiménez MÁ, et al (2011) Analysis of HLA-A, HLA-B, HLA-DRB1 allelic, genotypic, and haplotypic frequencies in colombian population. Colomb Med 41:336–343. https://doi.org/10.25100/cm.v41i4.725 <h3>Acknowledgements</h3> I have no acknowledgment to declare. <h3>Disclosure of Interests</h3> None Declared.